In recent air-sending devices and air-conditioning apparatuses, required capacity for use in large rooms has been increased. Accordingly, the air-sending devices are required a high rate of air flow. Furthermore, the air-sending devices and the air-conditioning apparatuses are required to be low power input and low noise level for energy saving and increased comfort. In some cases, the above requirements are satisfied by devising the shape of blades of fans.
Case (1) Noise reduction by matching a direction in which air flows into the gap between blades to an inlet angle of each blade (refer to Patent Literature 1, for example)
Case (2) Timing delay in occurrence of noise achieved by variation in outer diameter of a fan along the width direction of the fan (refer to Patent Literature 2 and Patent Literature 3, for example)
Case (3) Uniform air velocity distribution in an axial direction of an impeller achieved by varying the chord length in the axial direction of the impeller (refer to Patent Literature 4, for example)